5 Mar
2005
5 Mar
'05
4:40 p.m.
-------Original Message:
Date: Sat, 5 Mar 2005 12:41:50 -0600
From: "Randy McLaughlin" <cctalk at randy482.com>
Subject: Re: 8' drive on PC troubleshooting
From: "Geoff Reed" <geoffr at
zipcon.net>
Sent: Saturday, March 05, 2005 11:55 AM
veryify
are there any 8" drives out there that
don't require 24 volts to
work? I
have LOTS of powersupplies that supply GND, +5
and +12, but none
that also
supply +24 :(
To my knowlegde +5v & +24v are required by all 8" drives, other
voltages
vary from drive to drive. Before plugging in power connectors voltages.
Randy
If this is on an S-100 System (and if we're talking about 8"
drives, as opposed to the very rare 8' ones :), you can try
connecting the +24V line to the unregulated +18V.
From the installation instructions for the Quintec
Tophat, a
dual 8" (TM848 Tandon) drive assembly that fits across the top of
a Cromemco Z-2:
...Using a good DC voltmeter be certain that the +18V line is running
at least 18 volts, preferably higher, around 19 volts...
And if anyone really needs a +24V supply, I *might* have one or
two in the basement somewhere (+5, +12, +24). Not light, though,
as I recall...
mike
5 Mar
5 Mar
5 p.m.
And if anyone really needs a +24V supply,
...can't you take two bog-standard peecee power supplies and connect
ground of one to +12 of the other and get a 24V rail that way? I
*thought* the output side was supposed to be isolated.
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6:10 p.m.
And if anyone really needs a +24V supply,
...can't you take two bog-standard peecee power supplies and connect
ground of one to +12 of the other and get a 24V rail that way? I
*thought* the output side was supposed to be isolated.
7:25 p.m.
...can't
you take two bog-standard peecee power supplies and connect
ground of one to +12 of the other and get a 24V rail that way? I
*thought* the output side was supposed to be isolated.
Isolated from the power
line != isolated from ground I would not be at all suprised to find that the 0V
line on the output
side is in fact connected to mains ground. If that's the case, you
fairly obviously can't link 2 PSUs in series
I just picked up a handy not-currently-in-use PSU and opened it up.
The mains ground is connected to the chassis; the PC board mounting is
via metal standoffs, and they rest on solder pads which are connected
to the output ground wires. So you are correct - at least for that
supply, and I have no reason to think it exceptional.
But you probably could do fine, I'd guess, by just cutting the mains
ground connection for one or the other supply, as appropriate.
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6 Mar
6 Mar
2:44 a.m.
der Mouse wrote:
NNNGGHH!!! Danger! Crazy behaviour!
If you're really stuck for a 24V supply, you could try two smallish
deep-cycle batteries, like UPS or motorcycle batteries.
Gordon.
...can't you take two bog-standard peecee power
supplies and connect
ground of one to +12 of the other and get a 24V rail that way? I
*thought* the output side was supposed to be isolated.
Isolated from the power line != isolated from ground I would not be at all suprised to find that the 0V
line on the output
side is in fact connected to mains ground. If that's the case, you
fairly obviously can't link 2 PSUs in series
I just picked up a handy not-currently-in-use PSU and opened it up.
The mains ground is connected to the chassis; the PC board mounting is
via metal standoffs, and they rest on solder pads which are connected
to the output ground wires. So you are correct - at least for that
supply, and I have no reason to think it exceptional.
But you probably could do fine, I'd guess, by just cutting the mains
ground connection for one or the other supply, as appropriate.
11:13 a.m.
But you probably could do fine, I'd guess, by just
cutting the mains
ground connection for one or the other supply, as appropriate.
No, don;'t do that. FOr one thing most PSUs have a mains filter including
3 delta-connected capacitors. If you take off the ground wire, the
chassis wil try and float at half mains voltage (!). And for another
thing, if you have a component failure, you could end up with mains on
the case or output side, and the fuse won't fail. This will cook whatever
classic device you're powering from it, and may cook you too. Which is
more worrying depends on who you are!
-tony
5:29 p.m.
But you
probably could do fine, I'd guess, by just cutting the mains
ground connection for one or the other supply, as appropriate.
No, don;'t do
that. FOr one thing most PSUs have a mains filter
including 3 delta-connected capacitors. If you take off the ground
wire, the chassis wil try and float at half mains voltage (!). And for another thing, if you have a component
failure, you could end
up with mains on the case or output side, and the fuse won't fail.
Well, it depends on what happens when the other supply sees mains
voltage between its output 12V line and its ground line. But yes, this
may be a concern; you may want to find something like a nice hefty 15V
zener - one that can sink substantial current - and install it on the
output as a crowbar. Or perhaps a low-current 15V zener and a big-ass
SCR, the latter being the crowbar. Something of that ilk.
This will cook whatever classic device you're
powering from it, and
may cook you too. Which is more worrying depends on who you are!
:-)
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7 Mar
7 Mar
2:16 p.m.
But you
probably could do fine, I'd guess, by just cutting the mains
ground connection for one or the other supply, as appropriate.
No, don;'t do
that. FOr one thing most PSUs have a mains filter
including 3 delta-connected capacitors. If you take off the ground
wire, the chassis wil try and float at half mains voltage (!). And for
another thing, if you have a component failure, you could end
up with mains on the case or output side, and the fuse won't fail.
Well, it depends on what happens when the other supply sees mains
voltage between its output 12V line and its ground line. But yes, this
may be a concern; you may want to find something like a nice hefty 15V
zener - one that can sink substantial current - and install it on the 
5 Mar
5 Mar
6:46 p.m.
From: "der Mouse" <mouse at rodents.montreal.qc.ca>
Sent: Saturday, March 05, 2005 7:00 PM
Open frame power supplies that handle 8" drives (all of the "standard"
voltages) are cheap and easy to get (either jdr or jameco).
Randy
www.s100-manuals.com
And if anyone
really needs a +24V supply,
...can't you take two bog-standard peecee power supplies and connect
ground of one to +12 of the other and get a 24V rail that way? I
*thought* the output side was supposed to be isolated.
/~\ The ASCII der Mouse
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7232
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8 comments
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ard＠p850ug1.demon.co.uk -
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